WhenToBird

Sternula antillarum · Laridae

When Do Least Terns Arrive in Missouri?

Adult Least Tern
Photo: datadan, CC BY 4.0 via iNaturalist

Least Terns arrive in Missouri in mid May, peak in early August (1.6% of checklists), and most are gone by late August.

When to look

First arrivalsMay 15-21mid May
Common byMay 15-21mid May
PeakAug 1-7early August
Most gone byAug 22-31late August

Best: early August. First arrivals mid May; most are gone by late August. Peak: on about 1.6% of Missouri checklists.

  1. Jannot usually seen
  2. Febnot usually seen
  3. Marnot usually seen
  4. Aprnot usually seen
  5. Maycommon
  6. Juncommon
  7. Julpeak season
  8. Augpeak season
  9. Sepuncommon
  10. Octnot usually seen
  11. Novnot usually seen
  12. Decnot usually seen

Darker months: more checklists report it. Outlined: peak month.

0%0.5%1%1.5%2%Jan 1-7: 0% of 12628 checklistsJan 8-14: 0% of 9076 checklistsJan 15-21: 0% of 8790 checklistsJan 22-31: 0% of 11986 checklistsFeb 1-7: 0% of 8987 checklistsFeb 8-14: 0% of 10394 checklistsFeb 15-21: 0% of 15472 checklistsFeb 22-28: 0% of 9917 checklistsMar 1-7: 0% of 9877 checklistsMar 8-14: 0% of 9570 checklistsMar 15-21: 0% of 10274 checklistsMar 22-31: 0% of 16156 checklistsApr 1-7: 0% of 12774 checklistsApr 8-14: 0% of 14048 checklistsApr 15-21: 0% of 14894 checklistsApr 22-30: 0% of 23288 checklistsMay 1-7: 0.1% of 22645 checklistsMay 8-14: 0.2% of 21384 checklistsMay 15-21: 1.0% of 13989 checklistsMay 22-31: 1.3% of 15784 checklistsJun 1-7: 0.9% of 9691 checklistsJun 8-14: 0.7% of 9036 checklistsJun 15-21: 0.6% of 7907 checklistsJun 22-30: 0.7% of 9831 checklistsJul 1-7: 0.9% of 8008 checklistsJul 8-14: 1.4% of 7202 checklistsJul 15-21: 1.4% of 7151 checklistsJul 22-31: 1.8% of 9833 checklistsAug 1-7: 1.3% of 7639 checklistsAug 8-14: 1.5% of 7507 checklistsAug 15-21: 1.0% of 7429 checklistsAug 22-31: 0.6% of 11182 checklistsSep 1-7: 0.2% of 9471 checklistsSep 8-14: 0.1% of 8501 checklistsSep 15-21: 0% of 8169 checklistsSep 22-30: 0% of 11572 checklistsOct 1-7: 0% of 9028 checklistsOct 8-14: 0% of 9413 checklistsOct 15-21: 0% of 8656 checklistsOct 22-31: 0% of 11625 checklistsNov 1-7: 0% of 8627 checklistsNov 8-14: 0% of 8284 checklistsNov 15-21: 0% of 8075 checklistsNov 22-30: 0% of 10430 checklistsDec 1-7: 0% of 7870 checklistsDec 8-14: 0% of 7567 checklistsDec 15-21: 0% of 9696 checklistsDec 22-31: 0% of 13142 checklistsJanFebMarAprMayJunJulAugSepOctNovDec
Share of complete checklists reporting it, by week (4 per month). Grey bars: fewer than 10 checklists, not counted.

Frequency is the share of complete checklists in Missouri that listed the bird, 2016–2025. It is not a head count, and it follows where and when people go birding. How to read it.

JanFebMarAprMayJunJulAugSepOctNovDec
today
Second week of November

Each county is shaded by the share of complete checklists there that listed the bird, blended with the weeks either side. Darker is more often. It follows where people watch birds, not how many birds there are. How to read it.

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Where in Missouri

Best counties

Share of checklists at the peak
  1. Mississippi CountyBest early June · 22 checklists that week, 1,302 in all27%
  2. New Madrid CountyBest early June · 25 checklists that week, 1,138 in all23%
  3. Pemiscot CountyBest the second week of July · 36 checklists that week, 1,602 in all18%
  4. Perry CountyBest early August · 26 checklists that week, 1,583 in all18%
  5. St. Charles CountyBest mid July · 469 checklists that week, 33,508 in all18%
  6. Lincoln CountyBest late July · 68 checklists that week, 4,899 in all10%

Best spots

Share of checklists at the peak
  1. Alton SloughSt. Charles County, best early July · 88 checklists that week, 7,626 in all65%

Busy spots report more of everything; compare the checklist counts before you drive anywhere.

Best time of day

In Missouri, the Least Tern is most often listed on checklists started between 10 am and 12 pm (0.3% of those checklists).

0%0.5%12 am: too few checklists (205) to judge1 am: too few checklists (179) to judge2 am: too few checklists (204) to judge3 am: too few checklists (216) to judge4 am: too few checklists (630) to judge5 am: too few checklists (5072) to judge6 am: 0.3% of 27231 checklists7 am: 0.2% of 64162 checklists8 am: 0.3% of 67854 checklists9 am: 0.3% of 56515 checklists10 am: 0.3% of 47496 checklists11 am: 0.4% of 38845 checklists12 pm: 0.3% of 33383 checklists1 pm: 0.3% of 32503 checklists2 pm: 0.3% of 32615 checklists3 pm: 0.3% of 32514 checklists4 pm: 0.3% of 30274 checklists5 pm: 0.3% of 23446 checklists6 pm: 0.3% of 16374 checklists7 pm: too few checklists (10236) to judge8 pm: too few checklists (3133) to judge9 pm: too few checklists (722) to judge10 pm: too few checklists (405) to judge11 pm: too few checklists (261) to judge12a3a6a9a12p3p6p9p
Share of checklists started in each local hour that reported it. It reflects when people go birding as well as when birds are active. Grey hours have too few checklists (under 2% of the state’s, or under 200) to judge.
Week-by-week table
MonthDays 1-78-1415-2122-end
January0%0%0%0%
February0%0%0%0%
March0%0%0%0%
April0%0%0%0%
May0.1%0.2%1.0%1.3%
June0.9%0.7%0.6%0.7%
July0.9%1.4%1.4%1.8%
August1.3%1.5%1.0%0.6%
September0.2%0.1%0%0%
October0%0%0%0%
November0%0%0%0%
December0%0%0%0%

Neighboring states

  • Arkansas: arrives mid May, in the same week than Missouri
  • Indiana: arrives mid May, in the same week than Missouri
  • Oklahoma: arrives the second week of May, 1 week earlier than Missouri
  • Nebraska: arrives mid May, in the same week than Missouri

Common questions

When do Least Terns arrive in Missouri?
Least Terns arrive in Missouri in mid May, peak in early August (1.6% of checklists), and most are gone by late August.
When do Least Terns leave Missouri?
Most Least Terns have left Missouri by late August, when reports fall below half their usual rate.
When is the best time to see a Least Tern in Missouri?
The Least Tern is reported most often in early August, on about 1.6% of Missouri checklists.
Where in Missouri are Least Terns seen most often?
By county, Mississippi County, New Madrid County, and Pemiscot County have the highest peak reporting rates for the Least Tern (counties with at least 200 checklists).